how to get multiple values returned into table? without returning a table [lua]

Question

example

function func1()
 return 1,1,1,1
end

table = {}
table = func1()

print(table)

I don't want to do

 function func1()
  return {1,1,1,1}
 end

because the function im working with is already defined and I cannot modify it.

the desired output is

1 1 1 1

but this is not the case; it only returns the first value that the function returned.

How can I make this possible? Sorry for the bad formatting; this is my first time asking a question.

Also, I'm pretty sure the table is equal to an array? so sorry for that as well.

EDIT I don't know the number of arguments either.

Nifim · Accepted Answer · 2019-02-28 22:37:58Z

8

A function that returns multiple results will return them separately, not as a table.

Lua resource on multiple results: https://www.lua.org/pil/5.1.html

You can do what you want like this:

t = {func1()} -- wrapping the output of the function into a table
print(t[1], t[2], t[3], t[4])

This method is will always get all of the output values.

This method can also be done using table.pack:

t = table.pack(func1())
print(t[1], t[2], t[3], t[4])

by using table.pack you can discard nil results. This is can be helpful to preserve a simple check of the number of results using the length operator #; however it comes at the cost of no longer preserving the result "order".

To explain further, if func1 instead returned 1, nil, 1, 1 with the first method you receive a table where t[2] == nil. with the table.pack variation you will get t[2] == 1.

Alternatively you can do this:

function func1()
 return 1,1,1,1
end

t = {}
t[1], t[2], t[3], t[4] = func1() -- assigning each output of the function to a variable individually 

print(t[1], t[2], t[3], t[4])

This method can allow you to pick and choose where outputs go or if you want to ignore one you can simply do:

 t[1], _, t[3], t[4] = func1() -- skip the second value

edited Feb 28, 2019 at 22:37

answered Feb 27, 2019 at 23:44

Nifim

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2 Comments

Henri Menke Over a year ago

I recommend t = table.pack(func1()) instead of t = {func1()} because then you can query the number of elements in the table with t.n (#t won't work if there are “holes”).

Nifim Over a year ago

@HenriMenke added the table.pack variation to the answer, I still feel it can be a confusing result if you do expect internal nil values. in what i added to my answer, table.pack does not persevere the result. if the second result is nil then with table.pack the table you get has a t[2] that is not nil but is instead the value of result 3, and now t[3] is the value of result 4. if more then 1 result can return nil, table.pack makes it impossible to interpret the result

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